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Changes Trend in Chickenpox - Pregnant women and prevention with vaccine Changes Trend in Chickenpox - Pregnant women and prevention with vaccine

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  • 1. Changing Trends in Chickenpox – Pregnant Women and Prevention with Vaccine A A Gershon (USA) © 2000 The International Herpes Management Forum, all rights reserved.
  • 2. Varicella zoster virus: risks during pregnancy
    • Varicella zoster virus (VZV) is 25 times more serious in adults than in children:
      • 50 annual deaths in adults in the USA
    • No apparent risk of spontaneous abortion
    • Maternal risk probably highest in 3rd trimester:
      • reports of pneumonia requiring antiviral therapy
      • reports of fatalities
    • Risk to fetus and newborn due to maternal viraemia
    • Zoster not a problem (secondary infection)
    • Many susceptible adults in countries with tropical climate
  • 3.
    • Congenital varicella syndrome:
      • involvement of skin, limbs, eyes, brain, growth
      • pathogenesis unclear – possibly VZV reactivation in utero
      • 2% of offspring affected when maternal varicella occurs at Weeks 8–20
      • diagnosis difficult: PCR, ultrasound
      • no therapy, counselling difficult
    • Severe disseminated infection of the newborn
      • babies born 4 days or less after onset of maternal varicella
      • can be modified with VZIG given at birth
    • Asymptomatic at birth but early development of zoster
  • 4. Infant with fatal varicella
  • 5. Infant with congential varicella syndrome
  • 6. Infant with early zoster
  • 7. Varicella susceptibility by age, USA 1988–1994
    • Age (years) Susceptibility (%)
    • 6–11 14
    • 12–19 6.8
    • 20–29 4.5
    • 30–39 1.1
    • >40 1.3
  • 8. Live attenuated varicella vaccine
    • Developed by Takahashi over 25 years ago
    • Oka strain produced by attenuation during cell passage
    • Licensed for use in Japan and Korea 1989
    • Licensed in USA in 1995 for healthy susceptibles aged >1 year
    • Over 15 million doses distributed in USA:
      • 3 instances of transmission (mild contact cases)
    • Contraindicated during pregnancy:
      • 365 inadvertently vaccinated, no congenital varicella (CDC)
      • recommended for susceptible children of pregnant women
  • 9. Risk to pregnant woman if susceptible child in family is vaccinated/not vaccinated
    • Wild VZV (%) Vaccine (%)
    • Virus 7 100
    • Rash 100 5
    • Transmission 80 <1
    • Risk to mother <0.5 6
  • 10. Risk to infant if susceptible child in family is vaccinated
    • Assumes mother is susceptible
    • Assumes one child (double risk for two)
    • Assumes 2% risk of congenital syndrome
    • Assumes Oka causes congenital syndrome like wild type
    • Assumes Oka crosses placenta like wild type:
      • no documented viraemia in healthy vaccinees
    • Predict significantly lower risk to mother and fetus
  • 11. Safety and efficacy of varicella vaccine in adults and children
    • Adults require 2 doses to achieve >90% seroconversion
    • Vaccine extremely safe in children and adults:
      • rash in first 2 weeks may be wild type VZV
      • 5–10% mild rash 1–6 weeks (mean 4) after immunization
      • rare temporal association with severe adverse events (e.g. pneumonia, anaphylaxis, thrombocytopaenia)
    • 75–85% protection after household exposure to varicella
    • Rare zoster in USA vaccinees:
      • <30 cases, 2/3 Oka, 1/3 wild type VZV
    • Waning immunity not a significant problem
  • 12. Varicella vaccine: case-control efficacy study
    • 4 private practices in New Haven, CT, USA
    • 83 case-control groups
    • Varicella group: 14% vaccinated
    • Control group: 48% vaccinated
    • 85% efficacy after 2 years of 5-year study
  • 13. Leukaemic child with breakthrough varicella
  • 14. Vaccination of health care workers against chickenpox
    • 120 healthy adults, 19–45 years old
    • Vaccinated in USA 1979–1997
    • Most received 2 doses, 1–2 months apart
    • Average follow-up 5 years (range 1–20 years)
    • 12 cases break-through varicella (10%):
      • average 40 vesicles (<10 times expected)
      • 0.5–7 years after vaccination
      • Disease occurred in vaccinees who lost detectable antibodies to VZV
  • 15. Zoster in immunocompromised vaccinees after immunization Years after Vaccinees (%) Controls (%) immunization Leukaemia (Takahashi) 6 6 19 Leukaemia (Brunell) 6 0 21 Leukaemia (Hardy) 10 2 16 Renal transplant (Broyer) 10 7 13
  • 16. Varicella vaccine in USA CDC Draft: healthy people, 2010 goals
    • Reduce indigenous varicella in USA by 90%
    • Vaccine coverage >90% among children (19–35 months):
      • national level and all 50 states
    • Vaccine coverage >95% for children at school entry
    • Modelling indicates that fewer overall cases of varicella increased average age of onset:
      • however, as for measles in the USA, there will be fewer cases of adult varicella
    • There are already changes in epidemiology of illness in children
  • 17. Varicella vaccine: persistence of immunity
    • Duration of immunity never known with new vaccine
    • In USA, 5–10 year follow-up of >500 immunized healthy children:
      • over 90% remain seropositive
    • 20-year follow-up of 26 Japanese vaccinees:
      • 2 developed mild break-through infections, 100% seropositive
  • 18. Varicella vaccine: persistence of immunity
    • No apparent increase in rate or severity of breakthrough disease with time:
      • children (Johnson et al )
      • adults (Saiman et al )
    • Effect on varicella and zoster in absence of boosting from natural disease will require further study
  • 19. VZV: practical aspects for pregnant women
    • Identification of varicella susceptibles
    • History of disease >95% reliable
    • ELISA tests approximately 75% accurate:
      • false negatives > false positives
      • testing costs vary from US$1–40 per assay
      • other antibody tests limited availability (LA, FAMA)
  • 20. VZV: practical aspects for pregnant women
    • VZIG for pregnant susceptible women with close
    • exposures and selected offspring
    • To protect mother (impact on congenital syndrome?)
    • At birth if mother has varicella onset <5 days before delivery
      • or within 48 hours post-delivery
  • 21. VZV: practical aspects for pregnant women
    • Immunization of healthy, non-pregnant
    • varicella susceptibles in household
    • Pre-exposure (preferable) or post-exposure vaccination

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